Pipelayers are specialized vehicles used for installing large, heavy lengths of conduit into or above ground. Such conduits may be used, for example, to carry oil and gas from remote well locations over vast distances to a receiving station or refinery. In so doing, transportation costs for shipping, trucking or otherwise moving the oil and gas can be avoided. In addition to petroleum pipelines, pipelayers can also be used to install piping for other materials, or for installing of drain tile, culverts or other irrigation and drainage structure.
However, the installation of such pipelines is often very challenging. The locations of such oil and gas wells are commonly some of the most remote areas on earth, and the terrain over which the pipeline must traverse is often some of the most rugged. The climate of the installations can have very high or very low temperatures. The land may have significant elevational changes, and be subject to mudslides, severe weather, deep forestation and the like. In order to install the pipe, the pipelayer must be able to operate in all of the above-climate conditions, navigate over such terrain, and still be able to lift loads often in excess of 200,000 pounds.
Not only must pipelayers be able to handle such tasks, but given that the pipes are installed in long segments welded or otherwise secured together, they must be installed with great precision. The ends of the pipe being welded together must butt up against each other within a very tight tolerance. In addition, the pipes are often installed in connected fashion. This can result in a very long length of conduit (sometimes exceeding a mile) which must be laid into the ground in coordinated fashion. A series of pipelayers in such a situation will therefore be called upon to work in concert to lay the pipe.
When installing pipelines, if a natural or pre-made easement does not exist, a path through the terrain is first cleared through the forest, mountain pass or other geographical challenge at hand. A trench is then dug to the desired size, which is typically many feet deep and many feet wide. A right-of-way is also provided to one or both sides of the trench to allow for passage of trucks to transport the pipe into the location, and for passage of pipelayers to install the pipe. This right-of-way is ideally flat and sufficiently wide to easily accommodate the pipelayer but given the constraints imposed by the area topography and space availabilities of the local region or country, this may not always be the case. Pipelayers therefore often need to carry not only very heavy loads, but do so without being on level, stable ground.
Current pipelayers typically work on a track-type undercarriage and operate with a side-boom that can be extended at a variable angle to the chassis of the pipelayer. A cable is trained from a winch or other power source through a series of pulleys and terminates in a grapple hook or other suitable terminus. The grapple hook or other suitable terminus can then be secured to the pipe in such a way that when the winch recoils, the pipe is lifted. The boom arm is then extended and the pipelayer itself is navigated to a desired location for accurate installation of the pipe.
While effective, it can be seen that the weight of the pipe is positioned in cantilevered fashion away from the chassis, engine and undercarriage of the pipelayer. As the chassis, engine and undercarriage comprise the majority of the weight of a pipelayer, depending on the weight of the pipe being lifted and the length of the boom arm, the pipelayer can be subject to potential tipping and instability. Conversely, if the pipelayer is to be maintained in a stable position, the ability of the pipelayer to access the desired installation location can be significantly limited.
To offset these concerns, current pipelayers typically include a counterweight. The counterweight may comprise a series of heavy plates secured to a hinged structure such that through the use of a hydraulic cylinder or the like, the counterweight can be swung away from the chassis of the pipelayer on the side of the pipelayer opposite to the boom and thus counterbalance the weight of the load being lifted.
However, the counterweight systems of currently available pipelayers are operated entirely at the discretion of the operator and thus are arbitrarily applied. The operator of the pipelayer is able to extend the counterweight as he or she sees fit without regard to optimizing lifting capacity or stability of the pipelayer. Often, the counterweight is simply extended and left in that position during operation of the pipelayer. The lifting capacity and possible boom angle are therefore largely limited by such a fixed system.
Current demands being placed on pipelayer design, moreover, are requiring higher lifting capacities and boom lengths/angles. The pipelayer could in theory simply be made larger and heavier to satisfy these needs, but realistically the general footprint of the pipelayer is limited by cost, maneuverability, and transportation considerations. As stated above, pipelayers need to be operated in very remote and difficult locations. Once built, they need to be sent by rail and/or truck for use, and thus the size of those rails and trucks limit the upper end in terms of dimensions of overall pipelayer design. Even if they could be shipped to the location, they also have to be nimble enough to perform the job. Moreover, over-sizing the undercarriage and boom of the pipelayer will also increase manufacturing costs in terms of materials, and operating costs in terms of fuel.